1. Technical Field
The present invention belongs to the technical field of optical interconnection and relates to a photo detector, in particular to a photo detector consisting of tunneling field-effect transistors.
2. Description of Related Art
Compared with the traditional aluminum, copper has the following advantages: 1, the resistivity of copper is smaller (Cu: 1.7 μΩ/cm, Al: 3 μΩ/cm; 2, the parasitic capacitance of the copper interconnection is smaller than that of the aluminum interconnection; 3, due to low resistance, the power consumption of the copper interconnection is smaller than that of the aluminum interconnection; 4, the electro-migration resistance of copper is better than that of aluminum (Cu<107 A/cm2, Al<106 A/cm2), connection cavities generated by electro-migration are avoided, so that the reliability of the device is improved. Therefore, devices adopting copper interconnections are able to meet the requirements of high frequency, high integration, large power, large capacitance and long service life; and the traditional aluminum interconnection process is gradually replaced by the copper interconnection process.
With the further development of integrated electronic device technology, the power consumption and delay of copper interconnections also has gradually failed to meet demands, so the pursuit of technology with lower power consumption and faster interconnection is the future development trend. Compared with copper interconnections, optical interconnections have the advantages of high bandwidth and low loss, and have no problems in crosstalk, matching, and electromagnetic compatibility. The single-chip optical interconnection has been widely applied at present; in the future, the optical interconnection stands a good chance to replace the copper interconnection.
In the optical interconnection technology, the photo detector converts the optical signals and the electric signal plays the main role. Usually, the photo detector consists of p-i-n diodes. The basic structure is shown in the FIG. 1: a blocking layer (intrinsic layer), namely i layer 100b, is added between the p area 100a and the n area 100c of the common photoelectric diode, and light reaches the p area via an anti-reflection film 104. With a protective film 102 and electrodes 101, 103, when a high reverse bias is applied to the pn node, the blocking layer of the pn node produces photon-generated carriers under the light, and the photon-generated carriers are driven by the external bias to drift directionally so as to produce photo-generated current.
Due to the thick blocking layer, the node capacitance of the p-i-n diode changes are small and the blocking electric field becomes thicker, which enlarges the area for light absorption and light conversion, so the quantum efficiency is improved and the wavelength sensitivity is increased at the same time. However, the thickening of the blocking layer influences the response speed of the photo detector to a large extent, and the p-i-n diode requires a higher bias to make ionizing collisions appear in the diode, so the power consumption is increased.